fix: address review round four

- the cached-identity rung gains a finality gate: the identity value
  carries its descriptor seq and a cached row is served only when that
  seq lands in the child's own suffix, so a fork seed's replayed
  ancestor identity can never outrank the authoritative refold
  (stateVersion bumped for the state-shape change)
- the cold preparation validates the inspected header against the
  enumerated candidate's lifecycle witness; a republished id degrades to
  that child's corrupt diagnostic instead of leaking the new owner's log
- the new projection registration proves HMR disposal; companion notes
  qualify the superseded decision text and record the deliberate
  error-face asymmetry

packages/subagent/subagent/README.md

@@ -84,7 +84,7 @@ When `ctx.sessionProjections` is available, the service registers two projection
 
 ## Collection model
 
-The model-facing tool collects synchronously by default: it awaits the child result and disposes the run before returning. One-shot background delegation registers a plain Task in the tool, whose generic status, collection, and cancellation tools own later interaction, and persists its model-supplied `description` as the optional display label. Continuable background delegation calls `ctx.subagents.startContinuable()` and returns only the durable child id; the child owns its own turns from inbox acceptance, so there is no Task, no result promise, and no public subagent cancellation — a caller sends later work with the `send_message` follow-up tool, and the durable child Session remains the source of the child's detailed output. The continuation manager exists only while `ctx.agents` is available, and session persistence is resolved per continuation operation. Independently, `listChildren()` enumerates the live-preferred merge of the live session store and optional session persistence — live-only when persistence is absent, since a cold child cannot be resumed then either — and serves each child's durable mode/label from the registered `subagent` projection unit: the registry's watermark snapshot for a live child; for a cold one, a durable projection-cache row when the optional cache already serves the identity (immutable once appended, so staleness cannot matter), else one bounded-concurrency persistence inspection folded through the registry. A throwing cache read renders no verdict — the cache is derived data — and silently falls through to that authoritative re-fold. The projection fold is the single classification authority; listing parses no descriptor itself. A served identity produces a child row; a settled candidate whose fold served no identity is a `corrupt` diagnostic, a failed inspection is a transient `unavailable` retried on the next listing, and a running candidate without an identity yet is omitted (the creation window before its descriptor is appended). It never consults the continuation manager, Agent registrations, Activations, or providers. Each child row derives its read-time `hasChildren` hint from merged headers carrying durable `origin: 'subagent'`; it does not read descendant event logs, and the descriptor-backed child catalog remains authoritative when expanded. Service consumers such as a UI can retain both modes and choose a fallback for an unlabeled one-shot child; the model-facing `list_agents` tool projects only `continuable` entries and maps service activity to its existing `running`/`complete` vocabulary. The listing forwards the caller's signal to every persistence read, checks cancellation around each of those awaits, and reports every observed abort as `SubagentError` code `CANCELLED`; an unmounted projection registry fails loud with `SUBAGENT_CONTROL_PROJECTIONS_UNAVAILABLE`, and a missing session store with `SUBAGENT_CONTROL_SESSION_STORE_UNAVAILABLE`. See the [background subagent tasks Agent Note](../../../.agents/notes/implemented/feature/2026-07-08-background-subagent-tasks.md), the [continuable background subagents Agent Note](../../../.agents/notes/implemented/feature/2026-07-21-continuable-background-subagents.md), the [durable catalog Agent Note](../../../.agents/notes/implemented/feature/2026-07-22-durable-subagent-catalog-and-list-agents.md), the [merged-service Agent Note](../../../.agents/notes/implemented/simplification/2026-07-26-merge-subagent-control-service.md), the [capability-seam Agent Note](../../../.agents/notes/implemented/feature/2026-06-21-subagent-capability-seam.md), and `src/types.ts` for the complete contracts.
+The model-facing tool collects synchronously by default: it awaits the child result and disposes the run before returning. One-shot background delegation registers a plain Task in the tool, whose generic status, collection, and cancellation tools own later interaction, and persists its model-supplied `description` as the optional display label. Continuable background delegation calls `ctx.subagents.startContinuable()` and returns only the durable child id; the child owns its own turns from inbox acceptance, so there is no Task, no result promise, and no public subagent cancellation — a caller sends later work with the `send_message` follow-up tool, and the durable child Session remains the source of the child's detailed output. The continuation manager exists only while `ctx.agents` is available, and session persistence is resolved per continuation operation. Independently, `listChildren()` enumerates the live-preferred merge of the live session store and optional session persistence — live-only when persistence is absent, since a cold child cannot be resumed then either — and serves each child's durable mode/label from the registered `subagent` projection unit: the registry's watermark snapshot for a live child; for a cold one, a durable projection-cache row when it serves an own-suffix identity — its `seq` gate proves the value postdates the fork seed, where a child's own descriptor is immutable once appended — else one bounded-concurrency persistence inspection folded through the registry, whose result must still name the enumerated lifecycle (a re-published id degrades to a `corrupt` diagnostic). A throwing cache read renders no verdict — the cache is derived data — and silently falls through to that authoritative re-fold. The projection fold is the single classification authority; listing parses no descriptor itself. A served identity produces a child row; a settled candidate whose fold served no identity is a `corrupt` diagnostic, a failed inspection is a transient `unavailable` retried on the next listing, and a running candidate without an identity yet is omitted (the creation window before its descriptor is appended). It never consults the continuation manager, Agent registrations, Activations, or providers. Each child row derives its read-time `hasChildren` hint from merged headers carrying durable `origin: 'subagent'`; it does not read descendant event logs, and the descriptor-backed child catalog remains authoritative when expanded. Service consumers such as a UI can retain both modes and choose a fallback for an unlabeled one-shot child; the model-facing `list_agents` tool projects only `continuable` entries and maps service activity to its existing `running`/`complete` vocabulary. The listing forwards the caller's signal to every persistence read, checks cancellation around each of those awaits, and reports every observed abort as `SubagentError` code `CANCELLED`; an unmounted projection registry fails loud with `SUBAGENT_CONTROL_PROJECTIONS_UNAVAILABLE`, and a missing session store with `SUBAGENT_CONTROL_SESSION_STORE_UNAVAILABLE`. See the [background subagent tasks Agent Note](../../../.agents/notes/implemented/feature/2026-07-08-background-subagent-tasks.md), the [continuable background subagents Agent Note](../../../.agents/notes/implemented/feature/2026-07-21-continuable-background-subagents.md), the [durable catalog Agent Note](../../../.agents/notes/implemented/feature/2026-07-22-durable-subagent-catalog-and-list-agents.md), the [merged-service Agent Note](../../../.agents/notes/implemented/simplification/2026-07-26-merge-subagent-control-service.md), the [capability-seam Agent Note](../../../.agents/notes/implemented/feature/2026-06-21-subagent-capability-seam.md), and `src/types.ts` for the complete contracts.
 
 Continuable Activations await a best-effort final session flush without treating listener participation as durability confirmation. One-shot runs retain best-effort session checkpointing, so a completed one-shot child is discoverable after disposal only when its session actually reached persistence; the service does not invent a catalog entry from Task history when that checkpoint is absent.